1. Field of the Invention
The subject invention is related to a push button for a value input keyboard, having a keyboard base, on which, on the one hand, a guidance sleeve is molded and, on the other hand, detent or arresting means are constructed which serve for attaching the keyboard base to the printed circuit board. The push button further has a key or push-button head on which is molded a shaft for engaging the guidance sleeve, a pressure spring effective between the keyboard base and the push-button head, and stop means for limiting the stroke of the push button in the non-actuated state.
2. Description of Related Art
In a plurality of data acquisition and data processing appliances, value input keyboards, for example, ten-key clusters, alphanumerical keyboards or functional keyboards, are either integrated as autonomous components or are increasingly assigned as individual aggregates to be freely movable.
Requirements specifying error-free operability of the respective keyboards, ergonomic design of the push-button heads, geometrical optimization and unification of the push-button configuration, and as shallow a type of construction as possible, lead to an extensive standardization and thus to high quantities, which is a precondition for fabrication in large series and mechanized assembly.
The preferred structural concept of keyboards of this type involves installing functionally ready individual push buttons onto a printed circuit board acting as a carrier for the respective keyboard, preferably by means of suitable snap-in connections. Such a concept facilitates the build-up of random push-button configurations as well as changing them, it being easy to repair and also economical to produce even in small series.
Fabrication in large series and especially a mechanized assembly of keyboards requires, however, additionally, that the keyboard involved is produced with as few work steps as possible and with relatively simple components as far as molding technology is concerned, and that the assembly can occur without subsequent adjustment, and namely, with a high reproducibility as far as the alignment of the individual push buttons with respect to each other is concerned, customary fabrication tolerances and functional play between keyboard base and push-button head need generally not be reduced because of the plastic material guidance between the two components. Herein, we are not only dealing with as accurate an alignment of the keyboard bases of the individual push buttons as possible, but rather, especially, also with a respectively identical position of the push-button heads or their actuation surfaces in the unactuated state. This is indispensable particularly is keyboards are to be provided with printed legends in a touchless manner, for instance, with the use of a laser or similar energy beam.